Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Tumor resection has long been a mainstay of treatment for many kinds of cancers, such as sarcoma. For example, while many treatment protocols for sarcoma involve neo-adjuvant treatment with chemotherapy and radiation, a leading mode of sarcoma treatment in adults and children is primary tumor resection. The goals of resection include removal of the primary tumor to prevent local recurrence and metastases, preservation of normal tissue function, and in the majority of cases, preservation of skeletal and limb function. Tumor resection may also be a mode of treatment for other types of tumors.
In planning for tumor resection surgery, surgeons may consult images of the tumor that are produced using medical imaging techniques such as magnetic resonance imaging (MRI), positron emission tomography (PET), and computed tomography (CT). These images of the tumor show the boundary between the tumor and the surrounding normal tissue. Often, the boundary between the tumor and surrounding tissue is not well-defined. Instead, the tumor infiltrates into the surrounding tissue. Therefore, since leaving tumor mass in the body is associated with poor patient outcome, surgeons try to remove the tumor along with some surrounding tissue in an attempt to have no tumor left behind in the body.
To determine whether tumor was left behind in the body, a pathologist may examine and sample the edge of the removed tumor to determine if the tumor involves the surface (margins) of the specimen. The cut surface of the tissue mass (tumor and normal tissue) removed may be referred to as the “tumor margin.” When the entire tumor is removed with a generous covering of normal tissue on all surfaces, then the tumor resection specimen is said to be negative, or margins free of tumor. If the tumor is present at the edge of the mass, then the margins are said to be positive, or tumor involved. This implies that tumor is left behind in the body at these locations and the patient is at high risk for tumor re-growth (local recurrence) and shortened survival.
Often, tumor resection surgery is performed with a goal of a resected tumor that has negative margins. However, in some circumstances, surgery will result in a tumor with positive margins since the tumor sometimes infiltrates into the surrounding tissue making it difficult to determine the tumor boundary. In other circumstances, positive margins are a planned result of the surgery. For example, in sarcoma, because there is often little normal tissue surrounding the tumor, resection margins can have tumor 1-2 mm from the edge of the resection and are called “marginal” margins. Although a lack of tumor margin involvement in these types of resection cannot be assumed, tumor resections with marginal margins are sometimes performed to preserve a limb when amputation would otherwise be the alternative, among other situations.
While marginal margins cannot be avoided in every surgery, not all marginal margins are equal. By better understanding the nature of the tumor boundary, the marginality of the tumor margin can be reduced.